Stalling issue at idle

[JeepGuy93]

2003 Ford Explorer Eddie Bauer Edition 4.6L V8 4x4.

The stalling issue is most common at stop signs, when the vehicle is in drive and idling at operating temperature. It has occurred in park while cold, however. I immediately thought IACV since Fords have that issue, and it was shuddering a little before it stalled. I read the IACV% and it was only at 48%, which I understand to be a good value.

This vehicle also had a separate issue of a misfire, which shot a P0351 for a #1 coil fault. Looking at the plugs, they were crusty so I recommended new plugs, #1 coil, and a throttle body cleaning. I did all that with Motorcraft plugs, Denso coil, and a Hitachi IACV (I recommended replacement of the IACV rather than a cleaning). Misfire went away and the vehicle is more responsive.

However, the stalling issue continues. It seems to be more of an ignition/electrical shutdown rather than air cutoff (before I thought it could be a sticking or gummed up IACV). The battery light will come on, as well as the chime (similar to when you don't have your seatbelt on), and then stall. Then the CEL comes on and the rest of the dash lights come on.

There are no codes and no CEL. I read short term fuel trim and it was -3% on both banks, but I don't believe the car was at operating temp. On a side note, I ran an EVAP system test with my scanner and it failed.

Any knowledgeable suggestions or comments are appreciated. My next step will probably be reading fuel trim data as it stalls, but it is so intermittent.

 

[lincolnshibuya]

only use Motorcraft IAC, the rest are hit and miss.

 

[JeepGuy93]

In my experience, OEM parts, especially electronics, are relabeled by auto manufacturers, and are commonly manufactured by other companies. In this case, I researched the Hitachi IACV since it is labeled as the OEM part, and it seems that Motorcraft rebrands it. I've experienced this with Denso as well. The markings on the valves were identical. I do know brands to avoid, however, such as Airtex/Wells. They're bad out of the box 4/5 times.

With that aside, the stalling is sudden and immediate. It no longer shudders before it stalls. I've fixed vehicles that have stalled because of a lack of air, and it is a slow stall. This is why I'm leaning towards an electronic shutdown given the chime and how sudden the stall is, rather than air or fuel.

 

[swshawaii]

OP, even though you're leaning towards ignition without a CEL or trouble codes, this PCV vacuum elbow may be worth a look.

Rough idle and "Check Engine Soon" light - FIXED | Ford Explorer and Ford Ranger Forums - Serious Explorations

 

[JeepGuy93]

Thanks for the tip. I inspected all of the lines while I was in there, but obviously there could be a pinhole leak that can't be visually caught. Might be due for a smoke test.

What I meant by ignition or electronic shutoff, I didn't necessarily mean a fault in those systems, but rather the control module senses an issue and shuts down ignition. Sort of what that thread is about. What troubles me is that it's not shooting any codes.

I did spray carb cleaner to look for vacuum leaks, and ran a vacuum test. Vacuum was very strong. I'll look into those vacuum lines again.

 

[ROBinGa]

I agree with SWShawaii. Immediately after the IAC part there is an elbow of rubber hose and you must inspect the bottom of that elbow which is a known issue with cracking and causing the symptoms you describe. SyberTiger stared a great post on this problem with pictures. I will try to find that thread and copy you the link

 

[JeepGuy93]

You mean the thread linked above?

 

[ROBinGa]

This one too
http://www.explorerforum.com/forums...dle-and-check-engine-soon-light-fixed.217062/

 

[imp]

If you fail to find the root cause, and the stall is immediate upon placing transmission in any gear, but continues to run in P or N, go to the TCC. Problems there will be detected by PCM when vehicle is moving and possibly, but not cdertainly, when initial engagement stalls the engine, vehicle standing still. imp

 

[lincolnshibuya]

In my experience, OEM parts, especially electronics, are relabeled by auto manufacturers, and are commonly manufactured by other companies. In this case, I researched the Hitachi IACV since it is labeled as the OEM part, and it seems that Motorcraft rebrands it. I've experienced this with Denso as well. The markings on the valves were identical. I do know brands to avoid, however, such as Airtex/Wells. They're bad out of the box 4/5 times.

With that aside, the stalling is sudden and immediate. It no longer shudders before it stalls. I've fixed vehicles that have stalled because of a lack of air, and it is a slow stall. This is why I'm leaning towards an electronic shutdown given the chime and how sudden the stall is, rather than air or fuel.

in most cases here with IAC, hitachi != motorcraft

 

[JeepGuy93]

If you fail to find the root cause, and the stall is immediate upon placing transmission in any gear, but continues to run in P or N, go to the TCC. Problems there will be detected by PCM when vehicle is moving and possibly, but not cdertainly, when initial engagement stalls the engine, vehicle standing still. imp

The stall is not upon an immediate gear shift. Rather, it is sitting at a stop light, idling, in D with foot on brake. If would do this quite often in cold weather with engine hot. Out of about a dozen stalls I've personally witnessed, only about two were in park.

It sure would be nice if it shot a code... The misfire was easy, it shot a misfire code and I thought "oh great, a misfire" but the code, according to Chilton Library, can only be triggered by a faulty coil, a faulty, PCM, or a circuit short/open. Simple.

The battery light does come on whenever the chime is heard, but the alternator is putting out 14V. Battery is about 3 years old.

 

[imp]

Simple, but still unsolved.

 

[JeepGuy93]

Simple, but still unsolved.

The issue I fixed was simple. The cylinder #1 misfire.

 

[JeepGuy93]

UPDATE: Though it has always been intermittent, the stalling issue seems to be fixed. After the new IACV, I didn't clear the codes, and the issue continued. Once I reset the DTC, the issue has not reoccurred. I let it relearn the LT fuel trims and IACV%, and it's gone. Given that the issue has been off and on for years, and recently rendered the car difficult to drive, then stopped for a good few weeks, I believe this is a fix for the books.